1. Technical Field
The present invention relates to apparatuses for developing latent fingerprints and the method of use thereof, and in particular, to the use of a chamber in combination with a heat source and a sublimation system containing a mixture of cyanoacrylate and a sublimation dye wherein the application of heat transforms the mixture of cyanoacrylate and sublimation dye to vapor. In one embodiment, the vapor is circulated with a vapor circulating device which results in the quick and efficient development of latent fingerprints on objects contained in the chamber. In other aspects, a light source excites the sublimation dye causing photoluminescent emissions which are observable when viewed through an optical filter that in one aspect is integral with the chamber itself. In another aspect, the chamber includes a thermo cycling apparatus and a humidifying apparatus to recharge or rehydrate latent fingerprints.
2. Related Art
The primary component of a fingerprint is water—approximately 98%—which evaporates readily from a fingerprint and leaves a residue of various chemicals. The residue contains both inorganic and organic materials some of which can remain detectable on a surface long after the water component of the perspiration has evaporated. These chemicals include water soluble amino acids, peptides, salts, glucose, lactic acid, ammonia, riboflavin, and water insoluble oils and other sebaceous secretions (generally referred to as lipids). For the purposes of this application, the term “fingerprint” is used to describe the chemical residue left when a person touches an object, and/or the image formed by the residue.
The use of cyanoacrylate in the development of latent fingerprints on objects is well known and has been used as such for many years. Specifically, it is the reaction of the cyanoacrylate monomer and a catalyst that creates a microcrystalline vapor which adheres to fingerprints. Once the vapor cures, the cyanoacrylate forms a white polymer substance that reveals the fingerprint. To further enhance the detection of latent fingerprints, the cyanoacrylate monomer is mixed with dyes, specifically sublimation dyes, which upon excitation produce photoluminescent emissions. Such a mixture is disclosed in U.S. Provisional Application No. 61/010,491 entitled “Sublimation Dye Stained Co-Polymerization Cyanoacrylate,” which is hereby incorporated herein in its entirety.
U.S. Pat. No. 4,556,579 to Lowell discloses a kit for developing latent fingerprints wherein liquid cyanoacrylate monomer is deposited onto a porous fiber plug made of cellulose acetate fibers. The resulting fumes from the chemical reaction generate any latent fingerprints that come into contact with the fumes. The kit also has a solvent for removing such fingerprints when desired.
Similar to the '579 patent, U.S. Pat. No. 4,613,515 to Reggio also discloses a kit for developing latent fingerprints on a solid surface. The kit contains an absorbent pad impregnated with a cyanoacrylic polymerization catalyst and one or more initiators, a promoter and an accelerator. The kit also provides a separate source of a polymerizable alpha-cyanoacrylate monomer with at least one inhibitor agent. In operation, a cyanoacrylate monomer is added to the surface of the pad and the pad is placed adjacent a surface believed to contain a fingerprint. The pad remains undisturbed until it generates a microcrystalline vapor from the reaction of the cyanoacrylic catalyst and monomer. The vapor travels through the air to the solid surface wherein upon contact with the surface it adheres to the latent fingerprint, thereby making the latent fingerprint visible.
There are several disadvantages with the kits of the '579 and '515 patents. The user must physically add the cyanoacrylate monomer to a pad or plug which may result in unwanted spillage or a wrong amount of cyanoacrylate monomer applied to the pad. The kits also consist of multiple components which increases the complexity of using the kits as well as increases the amount of waste.
U.S. Pat. No. 5,342,645 to Eisele, et al. discloses a metal cartridge containing a porous or fibrous pad such as steel or glass wool, impregnated with a cyanoacrylate ester and a volatile, emissive lanthanide metal-complex or actinide metal-complex. Upon the application of heat, e.g., a butane-powered torch, the chemical reaction produces a chemical vapor that is used to develop latent fingerprints. The principal disadvantages with the '645 patent is that it requires a heat resistent housing and the use of a butane torch, both requirements making the cartridge clumsy and potentially dangerous to use. Further, the metal complex does not fully integrate into the polymer matrix, resulting in a vapor that is easily wiped off the developed fingerprint, making the transportation of delicate evidence difficult.
U.S. Pat. Nos. 5,348,759 and 5,424,092 to Weaver, et al. discloses a device for developing latent fingerprints. The device has a housing that contains a cyanoacrylate (either in liquid or solid form) and is adapted to receive a propane torch. Upon lighting the torch, the cyanoacrylate is vaporized and propelled toward the object to be tested on which any latent fingerprints appear within minutes. The user may replace the cyanoacrylate as needed for new tests. The disadvantage with these devices is that they require the use of a propane torch which increases the potential danger of using the devices. The devices also have multiple components including the need for additional cyanoacrylate to refill the housing, which increases the maintenance of the devices.
U.S. Pat. No. 5,395,455 to Bohanan discloses a method and apparatus for developing latent fingerprints on a portion of skin. The apparatus uses a heater to create a cyanoacrylate vapor which is propelled by a fan through a hose and comes in contact with skin. As seen in previous devices, this apparatus is very cumbersome to carry and use in field operation, and requires the use of a separate heater and fan which increases the maintenance effort.
U.S. Pat. No. 6,423,946 to Berka, et al. discloses an apparatus for developing latent fingerprints having a sealable container for depositing objects being tested for fingerprints. The container has an electrical heater as well as an exhaust means for evacuating air from the internal chamber. In operation, the method includes heating the container, placing objects within the chamber, adding a few drops of cyanoacrylate on an upper surface of an internal receptacle, covering the container, and pumping air from the container. After the fumes have developed any latent fingerprints on the objects within the chamber, the cover is removed and the objects are taken out. The disadvantage with the '946 device is that it is cumbersome to carry and use in the field. The user requires an electrical outlet for powering the heater. Also, the internal size of the chamber limits the number, size, and shape of the objects that can be placed in the container for testing.
Therefore, upon review of the prior art, there is a need for a simple, self-contained, re-chargeable apparatus for developing and visualizing latent fingerprints. There is a further need for such an apparatus to be mobile and easy to use, and having a containment system for directing the fumes or vapors toward and around the object being examined. There is a further need to enhance the detection of fingerprints by illumination of the developed fingerprints in combination with an optical filter to enhance the visibility of the illuminated fingerprints. The enhanced visibility offered by the current apparatus allows active monitoring of the polymerization process to ensure proper development levels to prevent overdevelopment, which can ruin the clarity of the fingerprint. There is a need to rehydrate or recharge dehydrated fingerprints in preparation for fingerprint development.